DE112009000551T5 - Exhaust line with a reagent injection device - Google Patents

Abstract

Exhaust line of a motor vehicle, wherein the exhaust line (1) comprises:
A conduit (3) having an injection section (7), the injection section (7) comprising an internal channel (17) for circulating an exhaust gas flow which is delimited by a side wall (13) and an upstream and downstream end (19, 21), the exhaust gas flow including central exhaust gas streams (27) in a central region of the internal channel (17) and peripheral exhaust gas streams (29) in the vicinity of the side wall (13);
- a reagent injector (5) mounted on the injection portion (7) and capable of injecting a reagent into the internal passage (17) according to an injection direction (F1);
characterized in that the internal passage (17) of the injection portion (7) has a central line L1 extending from the upstream end (19) to the downstream end (21), the conduit (3) being formed such that the central exhaust gas streams (27) from the upstream end (19) to the ...

Description

The The invention relates generally to exhaust gas trains of motor vehicles, with the facilities for injection of reagents such. B. Urea are equipped.

• – einer Leitung, die einen Einspritzabschnitt umfasst, wobei der Einspritzabschnitt einen internen Kanal zur Zirkulation eines Abgas-Flusses umfasst, der durch eine Seitenwand begrenzt ist und ein stromaufwärtsseitiges Ende und ein stromabwärtsseitiges Ende aufweist, wobei der Abgasfluß zentrale Abgasströme in einem zentralen Bereich des internen Kanals und periphere Abgasströme in der Nähe der Seitenwand aufweist,
• – einer Reagenz-Einspritzeinrichtung, die auf dem Einspritzabschnitt montiert ist und dazu geeignet ist, ein Reagenz gemäß einer Einspritzrichtung in den internen Kanal zu spritzen.

More specifically, the invention relates to an exhaust system of a motor vehicle with:

• A conduit including an injection section, the injection section comprising an internal passage for circulating an exhaust flow delimited by a side wall and having an upstream end and a downstream end, the exhaust flow having central exhaust flows in a central region of the internal one Having ducts and peripheral exhaust flows near the sidewall,
• A reagent injector mounted on the injection portion and adapted to inject a reagent into the internal passage in accordance with an injection direction.

One such exhaust system is intended to be an internal combustion engine equip, for. B. a diesel engine. It includes a catalyst, which is intended to carry out the reduction of nitrogen oxides, wherein the injection point upstream of the catalyst lies. The injector is intended to urea in Inject the exhaust line, the urea subsequently two subjected to chemical reactions, thermolysis and hydrolysis, and turns into ammonia. When the exhaust gases have a certain temperature At the heart of the catalyst, the ammonia reacts chemically with the nitrogen oxides, which reduces to water and nitrogen become.

The FR-A-2 891 305 describes an exhaust line whose line has upstream and downstream rectilinear sections which are connected by a helical intermediate section. It comprises an injection device whose injection direction substantially coincides with the main axis of the downstream-side portion. The exhaust gases originating from the helical intermediate section penetrate tangentially into the downstream section.

A such arrangement generates a high back pressure in the exhaust gas line, which is detrimental to the operation of the engine.

Furthermore The injected reagent drops are rotated by the exhaust gases offset and centrifuged against the walls of the exhaust pipe. In In certain cases, deposits can form and a premature oxidation of the walls of the exhaust pipe that can go to the point of perforation.

In In this context, the invention aims to provide an exhaust system to propose, whose operation is more satisfactory.

To For this purpose, the invention relates to an exhaust system of the beginning mentioned type, which is characterized in that the internal channel of the injection section has a central line, extending from the upstream end to the downstream side End, wherein the conduit is formed so that the central Exhaust gas flows from the upstream end to downstream end of the internal channel substantially circulating parallel to the central line, the exhaust line also comprises means to at least some of the peripheral Currents to impart movement through the internal channel, which rotates about an axis of rotation, in proportion Slightly inclined to the injection axis.

• – Der Einspritzabschnitt umfasst eine Ausbuchtung, die gegenüber der Seitenwand hervorsteht und eine Einspritzkammer definiert, die mit dem internen Kanal kommuniziert, und wobei die Ausbuchtung eine Einspritzöffnung aufweist, und wobei die Einspritzeinrichtung dazu geeignet ist, ausgehend von der Einspritzöffnung gemäß der Einspritzrichtung das Reagenz in den internen Kanal zu spritzen.
• – Die Mittel, um wenigstens einigen der peripheren Ströme eine Drehbewegung zu verleihen, umfassen eine Schnecke.
• – Die Schnecke umfasst einen schraubenförmigen Abschnitt, der durch die Ausbuchtung getragen wird, mit einer Achse, die gegenüber der Einspritzrichtung leicht geneigt ist.
• – Die Achse des schraubenförmigen Abschnitts bildet einen Winkel von weniger als 30° gegenüber der Einspritzrichtung.
• – Die Schnecke umfasst einen stromaufwärtsseitigen Abschnitt, der durch die Seitenwand getragen wird, wobei der Einspritzabschnitt eine Durchgangsfläche aufweist, die senkrecht zum stromaufwärtsseitigen Abschnitt der Schnecke größer ist als am stromaufwärtsseitigen Ende des internen Kanals.
• – Die Einspritzrichtung und die zentrale Linie des internen Kanals schneiden sich.
• – Die zentrale Linie ist eine Gerade.
• – Die Leitung umfasst einen stromaufwärtsseitigen Abschnitt und einen stromabwärtsseitigen Abschnitt, wobei jeweils der stromaufwärtsseitige und der stromabwärtsseitige Abschnitt stromaufwärtsseitige und stromabwärtsseitige interne Kanäle umfassen, die direkt mit dem stromaufwärtsseitigen und stromabwärtsseitigen Ende des internen Kanals des Einspritzabschnitts kommunizieren, wobei der stromaufwärtsseitige und stromabwärtsseitige interne Kanal zentrale Linien aufweisen, die gerade sind.
• – Der Abgasstrang umfasst einen Katalysator zur Reduktion der Stickstoffoxyde, der stromabwärts des Einspritzabschnitts liegt.

The exhaust system may have one or more of the following characteristics, which are to be considered individually or in accordance with all technically possible combinations:

• The injection portion includes a protrusion protruding from the side wall and defining an injection chamber communicating with the internal channel, and the protrusion having an injection port, and the injector adapted to receive the reagent from the injection port according to the injection direction to inject the internal channel.
• The means for imparting a rotary motion to at least some of the peripheral streams comprise a screw.
• - The worm comprises a helical portion, which is supported by the bulge, with an axis which is slightly inclined with respect to the injection direction.
• - The axis of the helical section forms an angle of less than 30 ° with respect to the injection direction.
• The screw comprises an upstream-side portion which is supported by the side wall, wherein the injection portion has a passage area which is larger perpendicular to the upstream-side portion of the screw than at the upstream-side end of the internal channel.
• - The injection direction and the central line of the internal channel intersect.
• - The central line is a straight line.
• The conduit comprises an upstream-side portion and a downstream-side portion, wherein each of the upstream-side and downstream-side portions has upstream and downstream internal Ka include channels that communicate directly with the upstream and downstream ends of the internal channel of the injection section, the upstream and downstream side internal channels having central lines that are straight.
• The exhaust line comprises a catalyst for reducing the nitrogen oxides, which is located downstream of the injection section.

Other Features and advantages of the invention will become apparent from the following detailed description, by way of example only and not limiting in any way with reference to the attached drawings, in which:

1 Figure 3 is a side perspective view of a drainage conduit adapted to receive a reagent injector, the injector being shown symbolically;

2 a perspective view of the line according to 1 is viewed from another direction;

3 one of the 2 is similar perspective view, with a part of the conduit being omitted to visualize the beginning of the screw, which allows to give a rotational movement to certain peripheral streams of the exhaust gas;

4 one of the 2 similar view, with an additional part of the line has been omitted to make the helical part of the screw visible;

5 one to 2 is similar perspective view, and wherein the course of various exhaust streams showing streamlines are placed over the figure.

In The following description is upstream and downstream relative to the normal circulation direction the exhaust gases.

The exhaust system 1 , the Indian 1 is partially shown, is intended to be mounted on a motor vehicle, which is equipped with an internal combustion engine, for. B. a diesel engine. The exhaust gas flow 1 comprises a catalyst for reducing nitrogen oxides (not shown), a conduit 3 located upstream of the nitrogen oxide reduction catalyst, and an injector 5 , which is intended to be a reagent in the line 3 inject.

The administration 3 includes, inter alia, an injection section 7 on which the injector 5 is mounted, a downstream side section 9 , which the injection section 7 with the nitrogen oxide reduction catalyst, and an upstream portion 11 located directly upstream of the injection section 7 located. The nitrogen oxide reduction catalyst is connected downstream to a tailpipe which allows the purified exhaust gases to be released into the atmosphere. The upstream section 11 is connected upstream with an exhaust manifold, not shown, which is intended to catch the exhaust gases emerging from the combustion chambers of the engine. Other equipment, such as As a catalytic cleaning element, or a particulate filter may be set between the manifold and the upstream portion of the conduit.

The sections 7 . 9 and 11 For example, the respective internal passages for circulating an exhaust gas flow, one being located in the extension of the other. The internal channel of the upstream section 11 is directly to the upstream end of the internal channel of the section 7 connected. The internal channel of the section 9 is directly to a downstream end of the internal channel of the section 7 connected.

The injector 5 is intended to inject into the internal channel of the injection section a mixture of water and urea in the form of droplets. The droplets mix with the exhaust gases by evaporating. The urea can be found in the section 9 chemical changes (thermolysis and hydrolysis), producing ammonia. The ammonia then combines with the nitrogen oxides in the catalyst to reduce nitrogen oxides and forms inert products (nitrogen and water) by chemical reaction.

As it is in the 2 can be seen, includes the injection section 7 a side wall 13 and a bulge 15 , The side wall 13 limits the internal channel 17 to the circulation of the exhaust gases inside. It has substantially circular straight cross sections. The side wall 13 includes near the upstream and downstream ends 19 . 21 a first diameter substantially equal to the diameter of the wall of the upstream and downstream portions. However, the sidewall has 13 in a central area 23 of the internal channel has a second diameter larger than the first one.

The bulge 15 stands in relation to the side wall 13 in front. It defines an injection chamber inside, with the internal channel 17 of the injection section communicates. The communication o The opening between the injection chamber and the internal channel has large dimensions. It covers the entire impression of the bulge on the side wall.

The bulge 15 has an injection port 25 on. The injector 5 is on the injection section 7 assembled. It is designed to receive the reagent from the injection port 25 according to the arrow F1 of the 1 specified injection direction in the internal channel 17 to inject.

The Injection direction is from upstream of the internal channel downstream and radially from outside to inside directed.

The internal channel 17 has a central line L1 extending from the upstream end 19 to the downstream end 21 extends. The line L1 passes through the geometric centers of each of the straight sections of the internal channel. At the in 1 illustrated embodiment, the line L1 is substantially straight. The injection direction F1 and the central line L1 intersect.

The sections 9 and 11 are also cylindrical, at least in end portions near the injection portion 7 , and in these sections include respective central lines L2 and L3, which are also straight. Lines L1, L2 and L3 are in alignment.

As it is in the 5 can be seen, the exhaust gas passing through the injection section has central exhaust gas streams 27 in a central area of the internal channel, and peripheral streams 29 near the side wall 13 of the internal channel.

To generate a rotational movement in the injection chamber, the exhaust line comprises means 31 to at least certain peripheral currents 29 a movement through the internal channel 17 to lend, which rotates about a rotation axis which is slightly inclined relative to the injection axis.

The means 31 include a snail 33 , The snail 33 includes an upstream-side intake part 35 passing through the sidewall 13 is worn, and a helical part 37 by the bulge 15 will be carried.

The snail 33 is open over its entire length to the internal channel or to the injection chamber. The upstream part 35 stands in relation to the side wall 13 in front. Accordingly, the injection section has 7 a passageway for the exhaust gases, which is perpendicular to the upstream side part 35 the worm is larger than at the upstream end 19 or on the upstream side section 11 , Accordingly, the exhaust gases are sucked. From this suction, the gases are accelerated and follow more easily the worm shape.

The part 37 is helical with an axis which is slightly inclined in relation to the injection direction. The axis forms an angle of less than 30 ° with respect to the injection direction. Preferably, the axis forms an angle of less than 15 ° with respect to the injection direction, wherein the axis z. B. coincides with the injection direction. The part 37 extends z. B. about 270 ° about its axis.

The part 37 stands opposite the bulge 15 out.

The helical part 37 has a substantially semi-circular cross-section. The cross section of the helical part decreases starting from the part 35 up to the part 35 opposite end 39 ,

It Now the operation of the exhaust line described above executed.

thanks a nitric oxide sensor determines the control computer the exhaust line the required amount of urea solution, which, after being converted to ammonia, the nitrogen oxides in to reduce the specific catalyst.

The injector 5 In accordance with the direction of injection F1, droplets are thrown out of a mixture of water and urea. The droplets are starting from the opening 25 cone-shaped ejected.

The exhaust gases collected by the exhaust manifold become the upstream side portion 11 channeled and penetrate through the upstream end 19 in the injection section. At the upstream end 19 are all the exhaust streams, both the central streams and the peripheral streams, parallel to the central lines L1 and L3. Because of the shape of the conduit, particularly the shape of the upstream section and the injection section, the central streams traverse 27 the injection section substantially parallel to the central line L1.

As it is from the 5 it can be seen, the central lines 27 when crossing the injection section 7 almost not distracted.

In contrast, the opposite to the upstream side part 35 the worm peripheral streams 29 in the snail 33 sucked, how to do it 5 extracts. This effect is all the more pronounced than the passage area provided to the exhaust gases, perpendicular to the upstream part 35 increases. The peripheral currents 29 that face other areas of the sidewall 13 do not circulate, are not in the snail 33 sucked.

The in the snail 33 entering exhaust gas flows pass through this to the opposite end 39 , These gas streams thus receive, in addition to their velocity component parallel to the central line L1, a rotational velocity component about the injection axis. Thus, these peripheral currents undergo a screw movement, with an axis which substantially corresponds to the direction of injection, or an axis which is slightly inclined with respect to the direction of injection. By slightly inclined is meant here that it forms an angle of less than 30 ° with respect to the direction of injection.

Thus, a gas jacket is created around the droplet cone, which prevents the liquid droplets from the walls of the bulge 15 to touch, at least near the injection hole 25 , The by the snail 33 aspirated gas streams continuously flush through the area near the opening 25 the liquid droplet. They thus prevent deposition of the liquid on the inner walls of the bulge between two successive injections.

Moreover, the injected liquid droplets are entrained around the direction of injection by the helical swirling motion of the gas streams, in particular the lightest droplets. The droplets are directed to the central exhaust streams. These central streams circulate parallel to the central line L1 and so do not tend to centrifugally trap the droplets on the sidewall 13 of the injection section to spin. In addition, this helps to improve the mixture between injected droplets and the exhaust gas.

Farther prevents the helical movement of the peripheral Exhaust gas flows around the injection direction around the training a vortex inside the bulge. In fact, could in the absence of this helical circulation the peripheral gas flows in the bulge an exhaust vortex form, which rotates about an axis perpendicular to the general Circulation direction of the exhaust gases runs, d. H. to the central Line L1. This vortex tends to contact the liquid droplets the inner walls of the injection chamber to spin and deposits to create. Solid amalgams can accumulate within the deposits consisting of urea and urea decomposition products, by crystallization. These deposits have a strong adhesion and can be reliable in the long term Counteract operation of the injector.

Farther are some urea decomposition products (cyanic or isocyanic acid, Ammelid, Ammelin, ...) very angry and can make a strong Corrosion of the walls of the injection chamber trigger.

Of the The exhaust system described above has even more advantages.

The Line can be obtained in a simple manner, in particular by Casting of the injection section.

The amount of helical movement of the gases around the injection direction can be easily calibrated. All you have to do is adjust the internal cross-section of the screw relative to the passage area of the internal channel. In this way one detects in the screw a more or less large part of the exhaust gases. For example, the helical part has 37 at the junction to the upstream part 35 a passage area of substantially 30% of the straight section of the internal channel.

Of the Exhaust line can be provided in numerous variants.

The Snail can turn clockwise or counterclockwise wrap around the injection direction.

The part 37 the screw surrounding the injection direction is not necessarily helical. It can form a spiral around the injection direction. It can also form a circle around the injection direction.

In each case has in the preferred embodiment of the invention the snail generally a snail shape, with one in proportion to the injection direction slightly inclined axis.

The Injector may instead of urea another reagent liquid inject, z. B. fuel.

The injector 5 can be of any type.

The central lines L1, L2 and L3 of the injection portion, the upstream-side portion and the downstream-side portion may be in alignment as described above. Alternatively, the respective central lines of the upstream and downstream side Ab be angled in relation to each other. Also, the center line of the injection portion may form an angle with the central line of the downstream-side portion and / or the central line of the upstream-side portion.

The central line of the injection section is not inevitable straight, but may have one or more slightly curved Sections include.

Of the Injection section may have one or more constrictions and one or more several extensions.

at a non-preferred embodiment cuts the injection direction not the central line of the injection section.

At this point, the injection section is understood to mean the pipe section extending upstream to the end of the upstream side part 35 the worm extends, and downstream to the downstream end of the bulge.

Summary

Exhaust line with a reagent injection device

The exhaust line comprises: a line ( 3 ) with an injection section ( 7 ) comprising an internal channel defined by a side wall, the exhaust gas flow having central exhaust gas streams in a central region of the internal channel ( 17 ) and peripheral exhaust flows near the sidewall; a reagent injection device ( 5 ) which is capable of injecting a reagent according to an injection direction (F1). The administration ( 3 ) is designed such that the central exhaust gas flows substantially parallel to the central line (L1) of the internal channel, wherein the exhaust gas line ( 1 ) Medium ( 31 ) for imparting to at least some of the peripheral streams movement through the internal channel which rotates about an axis of rotation which is slightly inclined relative to the direction of injection (F1).

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - FR 2891305 A [0004]

Claims (10)

Exhaust line of a motor vehicle, wherein the exhaust line ( 1 ) comprises: - a line ( 3 ) with an injection section ( 7 ), wherein the injection section ( 7 ) an internal channel ( 17 ) for the circulation of an exhaust gas flow passing through a side wall ( 13 ) is limited and an upstream side and a downstream side end ( 19 . 21 ), wherein the exhaust gas flow central exhaust gas streams ( 27 ) in a central region of the internal channel ( 17 ) and peripheral exhaust streams ( 29 ) near the side wall ( 13 ); A reagent injection device ( 5 ) located on the injection section ( 7 ) and is capable of injecting reagent into the internal channel according to an injection direction (F1) ( 17 ) to inject; characterized in that the internal channel ( 17 ) of the injection section ( 7 ) has a central line L1 extending from the upstream end ( 19 ) to the downstream end ( 21 ), wherein the line ( 3 ) is designed such that the central exhaust gas streams ( 27 ) from the upstream end ( 19 ) to the downstream end ( 21 ) of the internal channel ( 17 ) substantially parallel to the central line (L1), wherein the exhaust line ( 1 ) Medium ( 31 ) to at least some of the peripheral streams ( 29 ) a movement through the internal channel ( 17 ), which rotates about an axis of rotation that is slightly inclined relative to the direction of injection (F1). Exhaust tract according to claim 1, characterized in that the injection section ( 7 ) a bulge ( 15 ), which opposite the side wall ( 13 ) and defines an injection chamber that communicates with the internal channel ( 17 ) communicates with the bulge ( 15 ) an injection opening ( 25 ), wherein the injection device ( 5 ) is capable of starting from the injection port ( 25 ) according to the injection direction (F1) the reagent into the internal channel ( 17 ) to inject. Exhaust tract according to claim 1 or 2, characterized in that the means ( 31 ) for imparting a rotational movement to at least some of the peripheral streams ( 29 ) a snail ( 33 ). Exhaust tract according to claims 2 and 3, characterized in that the screw ( 33 ) a helical part ( 37 ) formed by the bulge ( 15 ), with a slightly inclined relative to the injection direction (F1) axis. Exhaust tract according to claim 4, characterized in that the axis of the helical part ( 37 ) forms an angle of less than 30 ° in relation to the direction of injection (F1). Exhaust line according to one of claims 3 to 5, characterized in that the screw ( 33 ) one through the side wall ( 13 ) carried upstream ( 37 ), wherein the injection section ( 7 ) has a passage area perpendicular to the upstream ( 35 ) of the snail ( 33 ) is greater than at the upstream end ( 19 ) of the internal channel ( 17 ). Exhaust line according to one of the preceding claims, characterized in that the injection direction (F1) and the central line (L1) of the internal channel ( 17 ) intersect. Exhaust line according to one of the preceding claims, characterized in that the central line (L1) is a straight line is. Exhaust tract according to one of the preceding claims, characterized in that the line ( 3 ) an upstream side section ( 11 ) and a downstream section ( 9 ), and wherein the upstream and downstream ( 11 . 9 ) have respective upstream and downstream internal channels directly connected to the upstream and downstream ( 19 . 29 ) of the internal channel ( 17 ) of the injection section ( 7 ), wherein the upstream and downstream internal channels have straight central lines (L3, L2). Exhaust line according to one of the preceding claims, characterized in that it comprises a catalyst for reducing the nitrogen oxides, which downstream of the injection section ( 7 ) is arranged.

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